The present invention relates to data processing by digital computer, and more particularly to address generation and cluster extension in distributed systems.
Data used by computer program applications is often structured as and represented by data objects, and applications generally write and read data objects to and from a database.
In a common data storage architecture, a data storage system includes one or more front-end servers (“front ends”), each of which communicates with a cluster of back-end servers (“back ends”). The back-end servers store data objects and are organized into one or more nodes or groups. A node is a group of servers that mirror each other, e.g., that contain the same database fragment. (The term “server” will be understood to refer to a back-end server unless the context indicates otherwise.) While technically a node can have only a single server, there should be at least two servers in each node to achieve high availability. The cluster is a potentially distributed system of back-end servers. The front-end server is a server that communicates with the back-end servers and operates to provide an interface between the cluster and applications.
Over time, the load on individual servers within the cluster will tend to increase. This is due to several factors, such as a reduction in the free capacity of each server as data objects accumulate on it, and more frequent accesses of each server by computer applications as more and more data objects are located on it. The capacity of the cluster will need to be expanded when the load becomes too great.
A common approach to increasing the capacity of a cluster is to add a new server to the cluster. This generally requires moving some data objects to the new server, which can involve rehashing the database. This is especially problematic in object-oriented databases, where the data objects must be identified by an object identifier that does not change during the lifetime of the data object.